Fast and accurate quality inspection of permanent magnets is increasingly important in development and production of electric drives. Parameters such as cogging torque, efficiency and power are directly influenced by the quality of permanent magnets in an electric drive. Moreover, recent price increases of rare earth materials force e-drive developers and manufacturers to use these precious materials in an efficient way, minimizing the amount of wasted magnet material, in other words, get the most performance out of the least amount of magnet material, meaning each magnet needs to conform to strict quality demands.
In order to accurately determine the full magnet quality, different magnet parameters need to be measured in an economic way, such as the remanence magnetization vector and its angular deviation, magnet homogeneity, material defect presence, magnetization deviations etc. With the increasing use of electric drives in automotive applications, an economic magnet inspection solution is needed, that is not only capable of measuring all these critical magnet characteristics, but also is compatible with automated production of electric drives. This means that the inspection solution must be fast, give quantitative results for all of the above mentioned magnet properties and be easily implementable in production lines. Classical magnetic measurement techniques fail to simultaneously deliver on all of the above mentioned requirements, either because they are too slow, only measure a single magnet property, are not digital etc.
A magnetic measurement system is known, also referred to as a magnetic field camera, which is an advanced magnet inspection technology for all kinds of permanent magnets, including uniaxial and multi pole magnets in various applications. The magnetic field camera technology is based on mapping the magnetic field distribution of a magnet using a plurality of magnetic field sensors.
In European patent application EP1720026, an example of such a magnetic field camera, also called a magnetic camera module, is described.
In European patent application EP2508906, an arrangement is described for characterizing magnetic systems based on an initialized set of input parameters of the magnetic system, the arrangement comprising:                means for measuring the magnetic field distribution, typically embodied as a magnetic camera module, and        means for determining an optimal expected magnetic field distribution of the magnetic system.        
In practice however, there exists an industrial need for improved devices and methods for characterising magnetic systems in an automatic way, especially magnetic systems comprising relatively large surfaces, which can be typically larger than the size of existing magnetic camera modules.